Andromeda & Triangulum Galaxies (M31 & M33)

The Andromeda and Triangulum galaxies (or M31/M33) are the nearest large spiral galaxies to our Milky Way. A third of M31 and all of M33 were observed from the UV to the infrared with Hubble by the Panchromatic Hubble Andromeda and Triangulum (PHAT) Treasury programs (PI Dalcanton).

Carbon Stars

I am PI of three followup Hubble program aimed at studying the carbon stars in both galaxies.

GO-12862: A pilot program to test the efficacy of the medium band infrared filters (F127M, F139M, and F153M) in distinguishing carbon and oxygen-rich stars. We found a conspicuous lack of carbon stars in the field observed. The results are summarized in Boyer et al. (2013).

GO-14072: Given the success of the pilot program, we observed 20 fields across the PHAT coverage in M31 using the infrared medium-bands. We found a dramatic decrease in carbon star formation towards the bulge that cannot currently be explained by models. See Boyer et al. (2019)

GO-15932: In Cycle 27, our program to image additional fields in both M31 and M33 with the infrared filters was approved. Observations are expected in 2020.